There is mounting evidence of the role of dietary magnesium (Mg) in the distribution of other electrolytes (namely sodium (Na) and potassium (K)) in cardiovascular tissue. Magnesium deficiency is known to alter the contractile state of vascular smooth muscle and is implicated in myocardial infarction, particularly in sudden death following infarction. Certain diseases such as hypertension are not necessarily caused as a result of Mg deficiency, however, they may show alterations in their pathogenesis as a result of changes in Mg concentration. Magnesium appears to be the neglected ion of the cardiovascular system. There is a paucity of information concerning the effects of Mg on Na and K in the cardiovascular system and also Mg kinetics. The objective of this work is to use a method based on radioactive isotopes and digital computer simulation for quantitative information about content, intracellular (IC) and extracellular (EC) distribution and kinetics of electrolytes (Na, K, and Mg) in cardiovascular tissue of normotensive and spontaneously hypertensive rats as they are affected by different levels of dietary Mg. It is hoped that the proposed investigation may lead to better understanding of the role of Na and K as influenced by Mg in the development and history of cardiovascular disease. By this knowledge we hope to contribute to the understanding necessary for treatment of these disorders.